The present invention relates to a gas turbine for cooling moving blades using a refrigerant, a gas turbine apparatus, and a refrigerant collection method for gas turbine moving blades.
The combustion temperature of a gas turbine has a tendency to increase year by year so as to increase the efficiency and particularly the moving blades which are exposed to combustion gas become high in temperature, so that it is necessary to let a refrigerant flow in them and cool them.
As a refrigerant, compressed air extracted from a compressor, vapor generated by exhaust heat of combustion gas or the like is used.
To improve the efficiency of a gas turbine, it is important to collect and use a refrigerant after cooling the moving blades of the turbine in addition to realization of a high combustion temperature. Therefore, the so-called closed circuit cooling structure that the refrigerant flowing path is a closed circuit, for example, as described in Japanese Patent Application Laid-Open 8-14064 is variously proposed.
The big problems of a gas turbine having such a closed circuit cooling structure are the stress due to centrifugal force caused by rotation of the gas turbine and the sealing property of the connection of the refrigerant flow paths installed in the configuration member of the moving blades and turbine rotor.
The reason for that the stress due to centrifugal force caused by rotation of the gas turbine comes into a problem is shown below.
The turbine rotor rotates at a very high speed round the center line of the turbine, so that remarkable stress due to the centrifugal force is generated in the outer periphery. Particularly the wheel has many moving blades in the outer periphery and the operating centrifugal force is extremely large, so that high strength is required. Generally, inside the configuration member of the turbine rotor, the refrigerant flow paths and others are installed and hence the configuration members are not uniform, so that the stress is concentrated at a specific part and there is the possibility that the strength decreases.